He added: "The focus now should be to stop them from going to industrial-scale production, to allow us to do a full-court-press inspection and to be sure they remain inside the treaty."

His remarks will serve to increase the pressure on the US, British, French, German and Russian governments, whose collective efforts to halt Iran's nuclear research have so-far failed, says BBC diplomatic correspondent Jonathan Marcus.

Last month the agency revealed the main nuclear plant at Natanz was using about 1,300 centrifuges - machines that spin uranium gas into enriched material.

Until recently, those centrifuges were incapable of running at the speeds necessary to make nuclear fuel.

However, the material being produced by Iran still requires further enrichment before it can be turned into bomb-grade material.

More sanctions threatened

Mr ElBaradei has previously said that Iran would not be able to produce the highly enriched uranium needed for a nuclear bomb as long as it remained under the supervision of IAEA inspectors.

The agency is due to report its findings to the UN Security Council next week.

The UN Security Council has imposed sanctions on Tehran for its failure to scale back its nuclear programme.

Nicholas Burns, the US undersecretary of state for policy, told the New York Times that if Iran does not agree to suspend its activities by the time of next month's G8 meeting, the US would press for a third round of sanctions.

Tehran has insisted that its nuclear programme is for peaceful purposes only.